Electrochemical oxidation of glucose at nanoporous black gold surfaces in the presence of high concentration of chloride ions and application to amperometric detection

The electrochemical oxidation of glucose on nanoporous black gold (NPBG) surfaces, prepared by an anodization of pure gold in oxalic acid, was investigated in the absence and presence of Cl−. The porosity of the NPBG layers was controlled by changing the step time for the anodization process, and the dependence of glucose oxidation on the electrochemical surface area (ESA) of the NPBG layers was systematically examined. The current density for glucose oxidation on NPBG surfaces in the absence of Cl− does not increase linearly with ESA because glucose oxidation reactions cannot fully utilize the entire surface of the porous Au layers at higher ESAs. In contrast, the current density for glucose oxidation increases more linearly with ESA as the concentration of Cl− increases, and with Cl− concentration of 100 mM a linear relationship between the current density and ESA of NPBG surfaces was observed. This indicates that the expansion of porous layer in NPBG is directly associated with the increase in the current density for glucose oxidation in high concentrations of Cl−. Detailed mechanism for glucose oxidation on NPBG surfaces depending on the ESA of the NPBG and Cl− concentrations was discussed, and the application NPBG to the amperometric detection was demonstrated.